Oil on spark plug.

[Macflurry]

Evening guys.

I'm having a bit of an issue with one of my plugs coming up covered in oil and subsequently making my bike (M900) run like a dog!!

When I got the bike and set up the carbs I noticed one of the plugs was heavily covered in oil which was causing the bike to pop and bog when revv'd. I also noticed metal filings in the oil when I dropped it to remove the oil filter.




Cleaned them both up and it ran great in the garage while setting the carbs up. Just before taking it out, the bike ran out of fuel while it was ticking over (rust blocking fuel from the tank) and ran like crap when more fuel was put in. De-rusted the tank and cleaned everything out, including the carb's. When setting them up I noticed that it was still running rough, checked the plugs and the same one was fouled up just from time running in the garage.



Put a fresh set of plugs on and everything was great. But after a minutes just checking the carbs were set up I had started getting a small amount of oil on the one plug.



Doesn't show it up too well but just so you can see the state changes as it goes.

Took the bike out for two hours, three days ago, parked it up in the garage and then went to look at it today before going out again. Checked the oil and the plugs before setting out. On the two hour run the oil had dropped from 3/4 of the way up from Min to Max down to about 1/4 and the same plug had a coating of oil. It was only a thin film of oil all over the electrode which looked more ingrained than stuck to it and made it look anodised shiny black.

Gave it a quick clean and rode it into town to pick up some more spark plugs as backups. As soon as I set off it was popping through the rev's. As I got to town it had eased up so I thought that maybe what was left on the plug had burned off. Went from Frome to Glastonbury and about half way there it started getting worse again. Left it parked up and swapped the plug for one of the new ones after getting some lunch. Once again, same plug covered in oil. This pic is just short of 3 hours use and had a quick clean about an hour previous.



Fresh plug in and it runs great... for 20 minutes.

So then, what's the best way to track down oil leaks into the chambers?

A quick google said to carry out a leak down test and listen for air leaking into the crank case for piston rings or into the head if it's valve seals. But I thought I would ask if there were any common issues to look into first before I started looking too deep into things?

Any advice on this is appreciated as I can see it being the head of at a minimum or full rebuild if it's the rings.